J/AJ/156/191 The ages of M31 star clusters: SED versus CMD (Fan+, 2018)
The ages of M31 star clusters: Spectral Energy Distribution versus
Color-Magnitude Diagram.
Fan Z., Li Z., Zhao G.
<Astron. J., 156, 191-191 (2018)>
=2018AJ....156..191F 2018AJ....156..191F (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Clusters, globular ; Abundances, [Fe/H] ;
Stars, ages ; Stars, masses ; Models
Keywords: galaxies: individual: M31 - galaxies: star clusters: general -
globular clusters: general
Abstract:
It is well-known that fitting Color-Magnitude Diagrams (CMDs) to
theoretical isochrones is the main method to determine star cluster ages.
However, when CMDs are not available, the Spectral Energy Distribution
(SED)-fitting technique is the only other approach, although it suffers
the age-metallicity-reddening degeneracy. In this work, we gather the ages,
metallicities, and masses of dozens of M31 star clusters from the
CMD-fitting with Hubble Space Telescope images from the literature for
comparison. We check the reliability of the SED-fitting results with
different models, i.e., Bruzual & Charlot (2003MNRAS.344.1000B 2003MNRAS.344.1000B) model
(BC03), Galaxy Evolutionary Synthesis Models (GALEV), and Advanced Stellar
Population Synthesis (ASPS) for the simple stellar populations (SSPs) with
single stars (ss)-SSP/binary-star (bs)-SSPs models. The photometry bands
includes the Galaxy Evolution Explorer GALEX FUV/NUV bands,
optical/near-infrared UBVRIJHK bands, as well as the Wide-field Infrared
Survey Explorer (WISE) W1/W2 bands. The comparisons show that the
SED-fitting ages agree well with the CMD-fitting ages, either with the
fixed metallicity or with the free metallicity for both the BC03 and
the GALEV model. However, for the ASPS models, it seems that SED-fitting
results are systematically older than the CMD ages, especially for the
ages log t<9.0 (year). The fitting also shows that the GALEX FUV/NUV-band
are more important than the WISE W1/W2 for constraining the ages, which
confirms the previous findings. We also derived the masses of our sample
star clusters from the BC03 and GALEV models and it is found that the
values agree well with those in the literature.
Description:
In order to compare the ages and mass estimates from CMD-fitting and that
from the SED-fitting, we gather a sample that has the CMD-fitting from HST
observations previously. The GCs of our sample are from the master catalog
of Perina et al. (2010A&A...511A..23P 2010A&A...511A..23P, 2011, J/A+A/531/A155). Perina et al.
(2010A&A...511A..23P 2010A&A...511A..23P) estimated the ages and metallicities of 19 star
clusters with the CMD-fitting method. The data is from HST/WFPC2 survey of
the bright young star clusters of M31. In order to analyze it, the ages and
metallicities of six star clusters from Perina et al. (2009, J/A+A/507/1375)
and four clusters from Williams & Hodge (2001ApJ...548..190W 2001ApJ...548..190W) are also
included. Perina et al. (2009, J/A+A/507/1375) used the HST/ACS archive data
and the solar abundance isochrone of Girardi et al. (2002A&A...391..195G 2002A&A...391..195G)
while Williams & Hodge (2001ApJ...548..190W 2001ApJ...548..190W) used observational data from
WFPC2 imager aboard the HST and the isochrone of Bertelli et al. (1994,
J/A+AS/106/275). Thus, the master catalog includes 29 GCs. In addition,
Perina et al. (2011, J/A+A/531/A155) gives the lower limits of ages for
three star clusters, B292, B337, and B350 by fitting the isochrones with
the observed CMDs, especially for the SGB stars. Our final sample consists
of 32 star clusters with ages and metallicities already derived using
the CMD-fitting technique.
Objects:
---------------------------------------------------------
RA (ICRS) DE Designation(s)
---------------------------------------------------------
00 42 44.33 +41 16 07.5 M31 = NAME Andromeda Galaxy
---------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 84 32 Ages of our sample star clusters derived from
SED fits of different passband combinations with
BC03 models and Padova 2000 stellar evolutionary
tracks
table2.dat 84 32 Same as Table 1 but for fixed-Z from
the literature
table3.dat 84 32 Same as Table 1 but for the GALEV models and
a Kroupa (2001MNRAS.322..231K 2001MNRAS.322..231K) initial mass
function (IMF)
table4.dat 84 32 Same as Table 3 but for fixed-Z from
the literature
table5.dat 84 32 Same as Table 1 but for the ASPS bsp-SSPs
models
table6.dat 84 32 Same as Table 5 but for fixed-Z from
the literature
--------------------------------------------------------------------------------
See also:
V/143 : Revised Bologna Catalog of M31 clusters, V.5 (Galleti+ 2012)
J/A+AS/106/275 : Theoretical isochrones (Bertelli+ 1994)
J/AJ/119/727 : M31 globular clusters photometry (Barmby+, 2000)
J/AJ/122/2458 : M31 globular clusters from HST (Barmby+, 2001)
J/AJ/123/2490 : RV and [Fe/H] of M31 globular cluster system (Perrett+, 2002)
J/A+A/416/917 : Revised Bologna Catalog of M31 globular clusters
(Galleti+, 2004)
J/A+A/449/143 : Photometry of M31 globular cluster candidates (Ma+, 2006)
J/AJ/133/2764 : M31 globular clusters structural parameters (Barmby+, 2007)
J/ApJS/173/643 : GALEX UV photometry of M31 Globular Clusters (Rey+, 2007)
J/A+A/507/1375 : HST/ACS VI data of M31 globular clusters (Perina+, 2009)
J/A+A/508/1285 : Metallicity estimates of M31 globular clusters
(Galleti+, 2009)
J/AJ/139/1438 : SED and age estimates of 104 M31 globular clusters
(Wang+, 2010)
J/A+A/531/A155 : HST photometry in six M31 globular clusters (Perina+, 2011)
J/A+A/544/A155 : HST photometry of M31 globular clusters (Federici+, 2012)
J/AJ/144/191 : Multicolor photometry of 135 star clusters in M31
(Wang+, 2012)
J/ApJS/199/37 : GALEX catalog of star clusters in M31 (Kang+, 2012)
J/AJ/146/135 : Physical parameters of 29 M31 globular clusters (Agar+, 2013)
J/ApJ/769/10 : Spectroscopy of M31 globular clusters (Jacoby+, 2013)
J/AJ/148/4 : JHK photometry of 913 globular clusters in M31 (Wang+, 2014)
J/ApJ/786/117 : M31 PHAT star clusters ages and masses (Fouesneau+, 2014)
J/ApJ/797/116 : Chemical properties of M31 star clusters (Colucci+, 2014)
J/AJ/152/208 : Ages and metallicities for M31 star clusters (Fan+, 2016)
Byte-by-byte Description of file: table[123456].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- ID Cluster identifier
13- 17 F5.2 [-] [Fe/H] [-1.7/0.4]? Metallicity (only in Tables 1,3,5)
(1)
19- 22 F4.2 [-] e_[Fe/H] [0/2]? Lower limit uncertainty in [Fe/H]
(only in Tables 1,3,5)
24- 27 F4.2 [-] E_[Fe/H] [0/1.51]? Upper limit uncertainty in [Fe/H]
(only in Tables 1,3,5)
29- 33 F5.2 [-] [Fe/H]P [-1.82/0.68] Metallicity from Perina et al.
(2010A&A...511A..23P 2010A&A...511A..23P, 2011, J/A+A/531/A155)
35- 39 F5.2 yr logt [7.3/10.14] Log age
41- 44 F4.2 yr e_logt [0/1.41] Lower limit uncertainty in logt
46- 49 F4.2 yr E_logt [0/1.44] Upper limit uncertainty in logt
51- 54 F4.2 yr logtP [7.4/9.8] Log age from Perina et al.
(2010A&A...511A..23P 2010A&A...511A..23P, 2011, J/A+A/531/A155)
56- 59 F4.2 yr e_logtP [0/0.3] Lower limit uncertainty in logtP
61- 64 F4.2 yr E_logtP [0.1/1.64] Upper limit uncertainty in logtP
66- 69 F4.2 Msun logM [3.4/5.49]? Log mass (not in Tables 5,6) (2)
71- 74 F4.2 Msun e_logM [0.01/0.73]? Lower limit uncertainty in logM
(not in Tables 5,6)
76- 79 F4.2 Msun E_logM [0/0.64]? Upper limit uncertainty in logM
(not in Tables 5,6)
81- 84 F4.2 Msun logMP [3.8/5.1]? Log mass from Perina et al.
(2010A&A...511A..23P 2010A&A...511A..23P, 2011, J/A+A/531/A155)
(not in Tables 5,6)
--------------------------------------------------------------------------------
Note (1): For the abundance of the Sun, Z=0.019 is applied for the models in
Table 1, Z=0.02 for the models in Tables 3 and 5.
Note (2): The Chabrier (2003PASP..115..763C 2003PASP..115..763C) initial mass function (IMF) was
adopted in Tables 1,2,5 and 6.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Tiphaine Pouvreau [CDS] 25-Mar-2019